Image sensors have become ubiquitous. They are widely used in digital still cameras, cellular phones, security cameras, as well as, medical, automobile, and other applications. The technology used to manufacture image sensors has continued to advance at a great pace. For example, the demands of higher resolution and lower power consumption have encouraged the further miniaturization and integration of these devices.
Pixel crosstalk currently limits performance of semiconductor image sensor devices. Ideally each pixel in an image sensor operates as an independent photon detector. In other words, electron/hole content in one pixel does not spill into neighboring pixels (or any other pixels in the device). In real image sensors, this is not the case. Electrical signals may move from one pixel to another. This crosstalk may increase the number of white pixels, reduce image sensor sensitivity, and cause color-signal mixing. Unfortunately, many solutions to crosstalk often exaggerate the effects of dark current or contribute to it. The combination of dark current and crosstalk may lead to appreciable image degradation.
Many techniques have been employed to mitigate the effects of crosstalk/dark current and enhance image sensor performance. However, some of these methods may not entirely eliminate the effects of pixel crosstalk and dark current.
Corresponding reference characters indicate corresponding components throughout the several views of the drawings. Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.